Pressure responsive switch unit



June 24, 1969 L. K. DUNN PRESSURE RESPONSIVE SWITCH UNIT Filed May a, 1967 INVENTOR LARRY K. DUNN BY fum ATTORNEY United States Patent 3,452,171 PRESSURE RESPONSIVE SWITCH UNIT Larry K. Dunn, Piqua, Ohio, assignor to Piqua Machine & Mfg. Co., Piqua, Ohio, a corporation of Ohio Filed May 8, 1967, Ser. No. 636,947 Int. Cl. H01h 35/24, 35/40 U.S. Cl. 200-83 13 Claims ABSTRACT OF THE DISCLOSURE This invention relates to improvements in pressure responsive switch units enabling them to be manufactured in a simple and economical manner yet producing a unit which is less subject to component wear and malfunction. The present switch unit further avoids the inherent undesirable characteristics of former units involving excessive tendencies to corrode and short circuit.

For purpose of illustration the invention is particularly described in reference to its application to submersible sump pumps but the invention and its application is obviously not so limited.

Though pressure responsive switches have been well known for a long period of time, it has proven extremely difiicult to produce a switch of this nature, particularly a submersible switch, which avoids maintenance and malfunction problems. For example, the problem of fluctuating internal pressure normally exists within the housing of such a switch. This produces an inherently unstable switching action and an inability of the switch to maintain a constant operation at specified desired pressure levels. In an effort to avoid this problem it has been proposed to vent the interior of the switch unit to the atmosphere. However, this produces other inherent disadvantages, namely excessive oxidation of parts and contacts and, quite frequently, short circuiting of the electrical mechanism. All of these difiiculties lead ultimately to wear and eventual jamming of the switch operating elements, resulting in complete unreliability of the switch unit.

The present switch provides a solution to all of the above problems. As distinguished from conventional switch units, the present unit is hermetically sealed to prevent entrance of moisture and other damaging foreign materials to its interior, yet provision is made for effectively maintaining internal pressure within the switch unit substantially the same as existing external atmospheric pressure. Furthermore, provision is made for the accurate adjustment of the operating elements of the switch unit so as to counteract variations in the tolerances of the various parts and their operating characteristics so as to enable dependable operation over the predetermined range of pressure differences to which the switch may be subjected.

The primary object of the invention is to provide an improved pressure responsive switch unit which may be economically fabricated, more eificient and satisfactory in use, adaptable to a wide variety of applications and unlikely to become inoperative.

A further object of the invention is to provide a switch unit in which the operating elements thereof are resiliently mounted, the degree of resilience provided being easily adjusted and readily controlled.

A further object of the invention is to provide a pressure responsive switch unit in which the high pressure control can be readily adjusted without affecting the adjustment and setting of the low pressure control and/or vice versa.

A further object of the invention is to provide a switch unit of the type described in which certain of the operating elements may be so balanced so as to compensate for variations in manufacturing tolerance and operating characteristics of other elements in the assembly.

A further object of the invention is to provide a pressure responsive switch unit possessing the advantageous structural features, the inherent meritorious characteristics and the means and mode of operation herein described.

With the above and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation as hereinafter described or illustrated in the accompanying drawings or their equivalents.

In the drawings which disclose one but obviously not necessarily the only embodiment of the invention:

FIG. 1 is a side view, partly in section and partly diagrammatic, of a typical installation of the pressure responsive switch unit forming the subject matter of the present invention;

FIG. 2 is a top view of the FIG. 3 is a side view being shown in section;

FIG. 4 is a fragmentary view showing the related accumulator in one extreme condition;

FIG. 5 is a fragmentary view showing the accumulator in the other extreme condition; and

FIG. 6 is a sectional view taken on line 6-6 of FIG. 3.

Like parts are indicated by similar characters of reference throughout the several views.

Referring to the drawing, FIG. 1 shows a typical installation of a pressure responsive switch unit incorporating the subject matter of this invention. In this type of installation the switch unit 1 provides a direct control of a submersible sump pump 2, both units being supported in the bottom of a sump or well 3 in which water collects for discharge to waste or elsewhere. Operating power for the pump 2 is supplied by a conventional power cord 4, the latter incorporating a breather tube 5. While FIG. 1 shows the pump 2 under the direct control of the switch unit 1, the switch unit may also be used for a remote control of the pump through a magnetic starter, contactor or relay system.

Referring ot FIG. 3, the pressure responsive switch unit 1 includes a housing 6 which forms a cavity open at its lower end. This cavity is closed by a flexible diaphragm 7 seated and sealed across the open end of housing 6 by means of a retaining ring 8 secured thereto by a plurality of bolts 9. A mounting flange 10 (FIG. 2) extends to one side of the retaining ring 8 and is secured to the base of pump 2 by means of bolts 11 (FIG. 1).

The composite unit comprising the pressure responsive switch 1 and the submersible pump 2 is lowered into the sump 3 with the pump base resting on the bottom of the sump. This places the bottom of the pressure responsive switch unit 1 below minimum or off water level within the sump 3 as indicated at X in FIG. 1. The diaphragm 7 closing the bottom of the switch unit 1 is therefore at all times submerged and is fully responsive to variations and fluctuations in pressure created by a rising and falling of the water level between minimum level X and the maximum or on level indicated at Y in FIG. 1. As the water level fluctuates between X and Y, the diaphragm 7 is subjected to fluctuating pressures. This in turn controls the operation of the switch within the unit 1 to selecswitch unit; of the unit with parts thereof tively energize and deenergize the submersible pump 2 at predetermined water levels.

A horizontally disposed mounting plate 12 is supported upon a pair of diametrically opposed projections extending inwardly from the interior wall of the housing 6. Depending from plate 12 is an adjustable pivot screw 13 which supports an oscillatory lever 14. The lever 14 is a narrow elongated blade element extending diametrically of the housing 6 and its pivoted end has an elongated slot accommodating the projection therethrough of the screw 13. Surrounding the pivot screw 13 and confined between the mounting plate 12 and the pivot end of lever 14 is a compression spring 15 which provides a resilient mounting and backing for the oscillatory lever 14 and atfords a bias thereof against the screw head.

Supported on the plate 12 adjacent the pivot screw assembly 13-15 is a bracket 16 to the lower end of which is secured a switch 17 having an operating plunger 18. Switch 17 is operated by application and release of pressure upon the operating plunger 18. This results from an oscillatory movement of the lever 14 which causes the energization and deenergization of the submersible pump 2.

Oscillatory lever 14 is maintained in resilient contact with switch operating plunger 18 by means of a series of springs acting in opposite direction. This series of springs includes not only spring 15 surrounding the pivot stud 13 but also springs 19 and 20 engaged with the free end of the lever 14. Spring 19, a tension spring, interconnects the remote free extremity of lever 14 with the mounting plate 12 and resiliently biases lever 14 in an upward or clockwise direction about its connection on pivot screw 13. Counteracting the influence of spring 19 is an adjacent coil type compression spring 20 hearing against lever 14 and maintained in proper position relative thereto by means of an interiorly projecting boss 21. The pressure desired to be exerted by spring 20 is controlled by adjustment of a threaded stud 22 carried in and vertically dependent from the mounting plate 12. The lower end of stud 22 is in a socket centrally disposed within a pressure plate 23 which centers and maintains the upper end of spring 20 opposite that engaged and centered by the boss 21.

Adjustment of the force created by spring 20 through manual adjustment of stud 22 provides accurate and precise control of the minimum or 011 water level X. Tension spring 19 continually exerts an upward pull on lever 14 tending to actuate therethrough the switch operating plunger 18. This continual force toward operation of switch plunger 18 counteracts any tendency of switch 17 to resist operation. Counteracting the tendency for the lever 14 to move in a clockwise direction is the force of spring 20 which resiliently urges lever 14 in the opposite or counter-clockwise direction about its resilient mounting on pivot screw 13. The pressure created by spring 20 not only counteracts the pull of spring 19 but also counteracts any sluggishness in outward movement of switch operating plunger 18 due to weak spring pressure within the switch 17.

Since it is practically impossible to obtain a plurality of switches 17 having the same operating characteristics with respect to ease or resistence to operation both to the on and 011 position the combination of springs 19 and 20 and the forces exerted thereby provide a means for readily compensating for variations in operating characteristics of switches 17. Spring 19 exerts a fixed or constant 'force in one direction while spring 20 provides a variable force in the opposite direction which enables accurate and minute adjustment of the operating characteristics of each switch unit 1 regardless of the operating characteristics of the individual switches 17 incorporated therein.

Control of the on or maximum water level Y is obtained by adjustment of a centrally located coil spring 24. This spring is confined between pressure plates 25 and 26, the upper pressure plate :being retained in position by a vertically dependent adjusting stud 27 supported centrally of the mounting plate 12. The lower pressure plate 26 is restrained against downward movement under influence of spring 24 by means of a peripherally engaged strap 28 also secured to the mounting plate 12. Thus, spring 24 is susceptible of compression within the confines of strap 28 but is restrained against unlimited expanding travel. The strap 28 provides a predetermined stop against continued expansion of spring 24.

Centrally fixed on the inner side of diaphragm 7 is a motion transmitting member 29. Extending transversely of member 29 and extending outwardly on both sides thereof is a pin 30. The projecting portions of pin 30 engage in recesses 31 which are located at approximately the midpoint of the oscillatory lever 14. Flexing of the diaphragm 7 therefore produces a reciprocatory motion of the member 29 and in turn oscillatory motion of the lever 14 about its resilient pivot on pivot screw 13.

Above pin 30 the member 29 extends through aligned openings in the lever 14 and the stop strap 28. Projecting from the end of member 29 is an extension 32 of reduced diameter. This extension projects through pressure plate 26 and provides a centering and locating means to maintain this pressure plate 26 properly centered with respect to pressure plate 25 and the adjusting stud 27. The otfset shoulder formed in the member 29 by the reduction of extension 32 is adapted to engage pressure plate 26. Therefore, upon movement of motion transmitting member 29, pressure plate 26 will be moved to alternately produce compression or expansion of spring 24 within the confines of the limiting strap 28.

The pivot point for oscillatory lever 14 is so adjusted that the lever 14 will not operate switch 17 until after the motion transmitting member 29 engages pressure plate 26 sufii-ciently to compress spring 24. Vertical adjustment of the pivot point to the desired position is accomplished by manual adjustment of the pivot screw 13 relative to the mounting plate 12. Upon proper adjustment of the pivot point for lever 14, compression spring 20 is then properly adjusted in relation to the internal actuating forces of switch 17 so as to compensate for variations therein. The on or maximum Water level Y is then established by adjustment of stud 27 and its associated pressure plate 25. This adjustment, affecting spring 24, determines the amount of external pressure or force required on diaphragm 7 to oscillate lever 14 suificient for operation of switch 17. Operation of switch 17 to its 11 position energizes the submersible pump 2 which remains energized until the oscillatory lever 14 moves in the opposite direction so as to permit actuation of switch 17 to its 011 position, whereupon the pump 2 is deenergized. The minimum external pressure or force applied to diaphragm 7, below which the diaphragm can flex so as to permit movement of lever 14 to the 011 position is determined by the pressure exerted on lever 14 by spring 20. When the external pressure on diaphragm 7 falls below the net pressure exerted on lever 14 by spring 20, spring 20 causes the lever 14 to move to its off position.

Subsequent adjustments of studs 13, 22 and 27 are possible without complete disassembly of the unit 1. Adjustment of stud 27 is readily accomplished by removal of plug 33 in the top of housing 6. To facilitate subsequent adjustment of studs 13 and 22, the housing 6 has a separate removable top portion 6a. Removal of screw studs 34 (FIG. 2) permits removal of the upper section 6a of the housing 6 whereupon studs 13 and 22 are readily accessible for adjustment.

The switch unit 1 cannot be completely sealed since it is necessary for the diaphragm 7 to move or flex relative to the housing 6. If the unit were completely sealed the diaphragm in moving to the on position would have to compress not only spring 24 but also the air inside the housing 6. This would require considerably greater force than would be normal and result in faulty switch operation.

To avoid this problem, the interior of unit 1 is provided with a breathing apparatus comprising breather tube '5 in the power cord 4 and what can be considered an accumulator 40 hermetically connected to the breather tube 5 by means of tube 41. The accumulator 40, preferably provided by a very light flexible airtight bag or balloon, is located within a protective open ended housing 42. The housing 42 may be located on any suitable support such as the power cord 4 as shown in the drawing. Since the protective housing 42 is open to atmosphere, the balloon 40 is subject to variations in atmospheric pressures. Inasmuch as the balloon 40 is hermetically sealed to the breather tube 5 and the interior of the unit 1, the interior atmosphere of the unit 1 is protected against entrance of moisture and other forms of foreign matter. Nevertheless, the condition of the balloon directly reflects atmospheric pressure. Thus air in unit 1 when subject to compression is perfectly free to travel up breather tube 5 and into the balloon 40, providing for its expansion to the extent permitted by atmospheric pressure. Such air may return to the interior of unit 1 upon flexing of the diaphragm in the opposite direction. Therefore there is no appreciable change in operation of the unit 1 due to changes in internal air pressures.

The accumulator 40 is preferably assembled to the breather tube 5 in a partially collapsed condition generally as shown in FIG. 1. By so doing, suflicient space is provided for expansion of the internal air as a result of increase in temperature. When so expanded the accumulator will be substantially completely dilated as shown in FIG. 4.

There is suflicient air Within the accumulator 40 at time of original assembly, however, to permit contraction of the internal air and a lowering of the pressure therein as a result of decrease in temperature. Under these conditions the accumulator is substantially completely collapsed as shown in FIG. 5. The accumulator still has the ability however to return to the condition as originally installed or to its fully dilated condition as a result of changes in either the surrounding atmospheric temperatures or as a result of changes in temperatures internally of the unit 1.

The accumulator 40 prevents direct communication between the interior of the unit 1 and the exterior surrounding atmosphere thereby preventing introduction of undesirable humidity and foreign materials to the unit 1. Simultaneously therewith it provides for equalization of the pressure inside unit 1 with the outside atmospheric pressure. This provides and insures uniform operating characteristics for the unit 1 throughout wide fluctuations of external conditions.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the stature the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise but one of several modes of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described my invention, I claim:

1. A switch unit comprising a housing, a switch means within said housing, means at least a portion of which is exposed to the exterior of said housing having an operating relation to said switch means and arranged to respond to changes in the physical environment to which the exterior of said housing is immediately exposed, further means in connection with the interior of said housing for reflecting therein physical conditions of a different environment, said switch means having in connection therewith means for selective operation thereof through the medium of said means at least a portion of which is exposed to the exterior of said housing and in correspondence with the existing differential of the physical environment interiorly of and immediately exterior to said housing.

2. A switch unit as set forth in claim 1 characterized by said means at least a portion of which is exposed to the exterior of said housing including a pressure responsive diaphragm which moves in direct correspondence with the pressure applied to the exterior of said housing and said further means in connection with the interior of said housing for reflecting therein said physical conditions of a different environment is pressure responsive and has in connection therewith means to reflect in the interior of said housing the existing pressure conditions in said different environment.

3. A switch unit as in claim 1 wherein said further means are relatively sealed from direct exposure to said different environment and have a direct connection with and a sealing relation to said housing.

4. Apparatus as in claim 3 characterized in that said sealed means is an expansible and contractible pressure sensitive medium defining a chamber normally having a partially collapsed state and responding to changes of the pressure condition of said different environment and having in connection therewith means to direct a corresponding change in the pressure conditions interiorly of said housing.

5. A switch unit as set forth in claim 4 characterized by said sealed means comprising an airtight expansible and contractible bag having in connection therewith a tube means which is hermetically sealed to the housing and said bag and opens thereto.

6. A pressure responsive switch unit as in claim 2 characterized by said switch operating means including a resiliently mounted lever having an adjustable pivot position, there being means normally resiliently maintaining the lever in contact with said switch means, said means a portion of which is exposed to the exterior of said housing having in connection therewith means to transmit a motion to said lever in correspondence wtih changes in the physical environment exterior to said housing as contrasted to corresponding conditions interiorly of said housing, said lever means being conditioned to engage and disengage said switch means at selected intervals of its plvoting movement.

7. A pressure responsive switch assembly as in claim 1 characterized by said means at least a portion of which is exposed to the exterior of said housing including a deflectable wall section of said housing, said further means in connection with the interior of said housingreflecting therein the pressure condition in said different environof said housing wall section, there being further means Within said housing for yieldingly resisting inward deflection of said wall section and in the instance of inward deflection storing energy for subsequently applying a force for return deflection thereof, said deflect-able wall section being responsive to the pressure conditions immediately exterior to said housing and the movements thereof being in correspondence with the differential of interior and exterior pressures reflecting changes in the physical conditions of the respective environments whereby said switch means will be energized and de-energized in a precise relation thereto.

8. A pressure responsive switch assembly including a switch housing submersible in :a body of fluid having a pressure responsive wall deflectable to and from a switch actuating position as the level of the liquid in which the housing is submerged reaches high and low levels respectively, a control unit for location in an atmospheric environment and including a flexible lbag containing a limited amount of gas and a breather tube in sealed communication at its opposite ends respectively with the interior of said housing and with the interior of said bag, said bag being normally partially collapsed and sensitive to atmospheric pressure and temperature, providing that the internal pressure in said housing is equalized to atmospheric pressure irrespective of the liquid level while precluding a free exchange of air between the housing interior and the atmosphere.

9. A pressure responsive switch unit including a housing having an inwardly deflectalble wall section, a snap action switch in said housing having differential motion requirements for operation and release, a lever means to actuate said switch, said lever means having a pivot mount, there being means rocking said lever in one direction on inward deflection of said wall section whereby to operate the switch, means applying a spring load in opposition to movement of said lever in said one direction, the last said means having a limited ability to follow a return movement of said lever in the opposite direction whereby said spring load is removed prior to release of said switch, and other relatively counteracting means applying another spring load to said lever effecting movement of said lever to release said switch in response to a predetermined outward return motion of said wall section.

10. A pressure responsive switch unit according to claim 9 characterized in that said last named means includes a fixed force extension spring urging said lever in said one direction and adapted to counteract too high a snap action switch release force, and a compression spring urging said lever in said opposite direction selectively adjustable variably to oppose said extension spring and to compensate for too low a snap action switch release force.

11. A pressure responsive switch unit according to claim 9 wherein the first said spring load applying means is a compression spring seated at one end on a fixed stop and adjustable at the other end for variable compression, said lever having a pivot adjustable so that said lever is capable of motion to encounter the load of said compression spring before the lever operates said snap action switch.

' 12. A pressure responsive switch unit according to claim 11 characterized in that said lever is pivoted at an inner end, is arranged to contact said switch and engage said compression spring at locations successively outwardly of said inner end and has said other spring load applied at the outer end thereof, there being means on said deflectable wall section adapted to contact said lever at an intermediate location substantially in line with said compression spring.

13. A pressure responsive switch unit according to claim 11 characterized by said switch housing being a sealed unit submersible in a body of fluid which moves between high and low levels and said sealed unit having in connection therewith a second unit for location in an atmospheric environment, said second unit including means continuously responding to atmospheric pressure conditions and means in sealed communication with the interior of said housing for continuously conditioning said interior to equalize the pressure therein with said atmospheric pressure.

References Cited UNITED STATES PATENTS 2,401,934- 6/1946 Hester 200-83 2,757,689 8/1956 Knox.

3,128,354 4/1964 Conery 200-83 3,187,135 6/1965 Singer ZOO-83.91

3,234,881 2/1966 Ekey 200-83 ROBERT K. SCHAEFER, Primary Examiner.

H. BURKS, Assistant Examiner. 

